This invention relates to a tone signal generation device prestoring sets of waveshapes of plural periods and generating a tone signal by reading them out in a suitable sequential order.
U.S. Pat. No. 4,383,462 discloses a tone signal generation device capable of producing a tone of high quality closely resembling a natural musical instrument by storing a full waveshape from the start of sounding of the tone to the end thereof in a waveshape memory and accessing this waveshape memory. For reducing the memory capacity which tends to become large in this type of device in which a full waveshape is stored in the waveshape memory, this U.S. Patent has adopted a technique according to which a waveshape of an attack portion is stored completely but as to a waveshape of subsequent sustain portion, a representative waveshape of one period or plural periods only is stored and this representative waveshape is read out repeatedly.
This system of repeatedly reading out a waveshape of one period has a problem that the tone color does not change timewise thereby giving a monotonous impression. The system of repeatedly reading out a waveshape of plural periods can more or less avoid such monotonousness but still cannot avoid monotonousness caused by repetition of the tone color change of the same pattern. There is also a problem that a periodical noise will occur in correspondence to a repeating period unless a fairly long repeating period is adopted.
It is, therefore, an object of the invention to overcome the problems of the periodical noise and the monotonousness of the tone color change due to the repeated reading in the system storing not waveshape data of a full waveshape but that of a partial waveshape of plural periods in a waveshape memory and thereby being capable of generating a tone signal of a relatively high quality using this stored waveshape and saving capacity of the waveshape memory.